Conventional opening and closing devices of an injection moulder are disclosed in Patent Literatures 1 and 2. the hydraulic or electric actuator is directly fixed on the movable platen and the fixed platen in the conventional opening and closing devices. Alternatively, the movable platen and the actuator includes the hooking part 61, which provided to the movable platen 3, and the end part of the operation rod 42, which includes a groove part fitting to the hooking part 61 to engage, as shown in FIGS. 16 and 17. In the configuration, the hooking part 61 and the end part of the operation rod 42 of the actuator 41 are connected with clearances S1 and S2 between the hooking part 61 and the end part 45 of the operation rod 42 of the actuator 41
Recently, speed of opening and closing operations becomes faster to improve productivity. When the opening and closing operation is speeded up, the side shoe 13, which is a movement guide of the movable platen 3, could be wore out prematurely. When this wear of the side shoe 13 progresses, the clearance between the side show 13 and the guide rail 11 is widen, triggering inclining and lateral sliding of the movable platen 3.
Also, the viscosity of the raw resin is reduced in order to make it easy to perform injection filling. When the viscosity of the raw resin is reduced, burrs tend to be formed. To prevent the formation of burrs, several countermeasures can be taken, such as increasing the mold locking force. When the mold locking force is increased, deformation of the movable platen and the fixed platen is exacerbated.
If the movable platen 3 is inclined due to the wear of the side shoe 13 or the fixed platen 2 and the movable platen 3 are deformed due to the increasing of the mold locking force, the wear of the side shoe 13 of the movable platen 3, the inclination of the movable platen 3, and the deformation of the fixed platen 2 and the fixed platen 3, cannot be absorbed solely by the clearances S1 and S2 between the hooking part 61 and the end part 45 even if the hooking part 61 and the end part 45 of the operation rod 42 of the actuator 41 were used as a connecting device between the movable platen shifting device 40 and the supporting part 60 fixed to the movable platen 3. As a result, deformation occurs in the connecting part of the operation rod 42 of the actuator 41 (shown as X2 in FIG. 18), leading to breakage of the operation rod 42 due to repeated bending.